The subject matter described herein relates generally to methods and systems for the control of noise emissions in wind turbines, and more particularly, to methods and systems for balancing noise emission and power production of wind turbines.
Generally, a wind turbine includes a turbine that has a rotor that includes a rotatable hub assembly having multiple blades. The blades transform wind energy into a mechanical rotational torque that drives one or more generators via the rotor. The generators are sometimes, but not always, rotationally coupled to the rotor through a gearbox. The gearbox steps up the inherently low rotational speed of the rotor for the generator to efficiently convert the rotational mechanical energy to electrical energy, which is fed into a utility grid via at least one electrical connection. Gearless direct drive wind turbines also exist. The rotor, generator, gearbox and other components are typically mounted within a housing, or nacelle, that is positioned on top of a base that may be a truss or tubular tower.
Some wind turbine configurations include double-fed induction generators (DFIGs). Such configurations may also include power converters that are used to convert a frequency of generated electric power to a frequency substantially similar to a utility grid frequency. Moreover, such converters, in conjunction with the DFIG, also transmit electric power between the utility grid and the generator as well as transmit generator excitation power to a wound generator rotor from one of the connections to the electric utility grid connection. Alternatively, some wind turbine configurations include, but are not limited to, alternative types of induction generators, permanent magnet (PM) synchronous generators and electrically-excited synchronous generators and switched reluctance generators. These alternative configurations may also include power converters that are used to convert the frequencies as described above and transmit electrical power between the utility grid and the generator.
Known wind turbines have a plurality of mechanical and electrical components. Each electrical and/or mechanical component may have independent or different operating limitations, such as current, voltage, power, and/or temperature limits, than other components. Moreover, known wind turbines typically are designed and/or assembled with predefined rated power limits. To operate within such rated power limits, the electrical and/or mechanical components may be operated with large margins for the operating limitations. Such operation may result in inefficient wind turbine operation, and a power generation capability of the wind turbine may be underutilized.
During normal operation, wind turbines with sophisticated control systems maintain constant speed and power by active blade pitch control. In addition, wind turbines have a controller which adjusts the pitch angle of the blade to optimize energy captured below rated winds and regulates power above rated winds. The controller may utilize a fixed fine pitch angle in the variable speed region and adjust the pitch in above rated wind speed depending on the power output and rotational speed of the turbine.
Although wind turbines do not emit greenhouse gases, a concern related to wind turbines is the emission of noise pollution. As such, the ability to control and/or manage perceived acoustic emissions of wind turbines facilitates integrating wind turbines into society.
Methods for reducing the noise emissions of wind energy systems have long been discussed. For example, it has been proposed to reduce aerodynamic noise caused by the blades through a speed/torque control of the system in order to keep turbine speed low during certain time intervals, e.g., during night time or other times in which reduced noise is desired. However, such derating greatly reduces the power production. Another proposed method to reduce noise emission is to reduce rotor rotational speed of certain wind turbines in a wind park individually, also referred to as “derating” the wind turbine in order to gain maximum overall performance of the system while meeting park noise constraints. Such selective derating of individual turbines permits a number of wind turbines to run at significantly higher speeds than the average speed of all the remaining turbines. This proposed solution provides greater power capture than a complete derating of the park, but provides reduced noise control and operation at reduced power coefficients.
It would be beneficial to provide a method and system in which the turbine can be controlled so that the trade-off between power production and noise level can be flexibly adjusted.